ALA Conversion to EPA and DHA: What Isotope Studies Show and Who Converts Best
Isotope tracer studies show the body turns only some plant ALA into EPA and very little into DHA. See what the studies measured, who may convert more, and where the debate stands.
Content last updated . This page has not been medically reviewed.
Quick answer
The body can turn plant ALA into EPA and then DHA, but in the tracer studies reviewed here the share is limited and varies from person to person. Reviews agree conversion to EPA happens but is limited in men, and that the further step to DHA is very low. [1] Whether that low conversion is enough for good health is debated. [2]
How scientists measure conversion
Isotope (tracer) studies give people ALA marked with a heavier form of carbon (13C), then track how much shows up later as labeled EPA, DPA and DHA in blood. Feeding studies instead raise ALA intake for weeks and measure blood or tissue levels. Both are indirect: they estimate whole-body conversion from blood samples, and results depend on the dose, the diet, the lab method and who took part. [3] An "estimated conversion" is a model result, not a direct count of fat made.What the studies found
| Study or review | Who and what | What it found | Strength |
|---|---|---|---|
| Burdge and Wootton, 2002 | Young women given a single 700 mg dose of labeled ALA, tracked 21 days | Estimated net conversion: EPA 21%, DPA 6%, DHA 9%; about 22% of the dose was breathed out as carbon dioxide in 24 hours [4] | Small tracer study |
| Williams and Burdge review, 2006 | Tracer and feeding studies | Adult men: conversion to EPA limited (about 8%), to DHA extremely low (below 0.1%); women: DHA conversion appeared greater (9%) [5] | Review of small studies |
| Burdge and Calder review, 2005 | Studies lasting weeks to months | More ALA raised EPA in blood and breast milk but not DHA, which may even fall at high ALA intakes [1] | Review |
| Brenna review, 2002 | Tracer studies | Whole-body conversion of ALA to DHA is below 5% in humans and depends on dietary omega-6 amounts; humans of all ages can do the conversion [3] | Review |
| Brenna and colleagues, ISSFAL 2009 | Healthy adults on typical Western diets | ALA or EPA supplements had little effect on blood DHA, while preformed DHA raised it [6] | Society review |
| Burdge opinion, 2022 | Re-reading the same evidence | Argues conversion may be nutritionally adequate; design differences and lack of replication preclude firm consensus [2] | Opinion |
Study amounts are study amounts, not advice. A single tracer dose does not describe what happens with a lifetime of eating.
Who converts best?
Evidence label: mixed. Sex: women show higher estimated conversion than men in several reviews, possibly because a smaller share of ALA is burned for energy and because of oestrogen, which these reviews describe as a possible effect. [1] The effect of oestrogen on DHA in pregnant and breastfeeding women "awaits confirmation," per one review. [5] Diet: conversion depends on how much omega-6 is in the diet. [3] Non-fish-eaters: in 14,422 UK adults, the estimated precursor-to-product ratio was higher in non-fish-eaters and in women, but this was a food-diary study with blood measures in a subgroup, and the authors say intervention studies are needed to confirm it. [7] Other factors such as genes, age, or health conditions: Proper evidence not found in the sources we read. We searched PubMed for tracer-study reviews and found no review that gave reliable, general figures by those factors. A validated test that tells a person their own conversion rate: Proper evidence not found.What this means for plant-based eaters
A 2026 systematic review of 45 studies found vegetarian diets, particularly vegan diets, had significantly lower blood EPA and DHA, and that DHA from microalgae oil improved DHA status, especially in pregnancy and lactation. [8] The same review says the evidence is limited by differences in design and dietary reporting. [8] If you eat little or no fish, a dietitian or clinician can help you decide whether an algal oil makes sense; this is especially worth asking about in pregnancy. See algal oil and omega-3 for vegetarians and vegans.Flaxseed and other ALA sources
Flaxseed, chia and walnuts supply ALA. [9] Because ALA mainly raises EPA and not DHA, ALA foods and fish or algal oils answer different questions. [6] Food pages: flaxseed, chia seeds and walnuts.Frequently asked questions
How much ALA becomes EPA and DHA?
It varies by study. One tracer study in young women estimated EPA 21% and DHA 9%, while a review of studies in men put EPA at about 8% and DHA below 0.1%. [4][5]
Do women convert more ALA than men?
Several reviews say estimated conversion is higher in women, though the pregnancy effect awaits confirmation. [1][5]
Can I test my own conversion?
Proper evidence not found. We looked for validated personal conversion tests in the sources we read and found none.
Does flaxseed oil raise DHA?
Reviews found ALA raises blood EPA but little or no DHA. [6][1]
Is low conversion a health problem?
That is debated. One 2022 opinion argues conversion is nutritionally adequate, while a 2026 review found lower blood EPA and DHA in vegans. [2][8] Ask a clinician or dietitian about your situation.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and limits
ALA foods are ordinary foods, but flaxseed oil and other concentrated products are supplements, and anyone on blood thinners, pregnant, or planning surgery should ask a clinician or pharmacist. See medication interactions. Supplements vary in quality; see quality testing. The general comparison is on ALA, EPA and DHA.
References
- Burdge GC, Calder PC. Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reprod Nutr Dev 2005. Read 2026-10-23.
- Burdge GC. alpha-Linolenic acid interconversion is sufficient as a source of longer chain omega-3 PUFA in humans: an opinion. Lipids 2022. Read 2026-10-23.
- Brenna JT. Efficiency of conversion of alpha-linolenic acid to long chain n-3 fatty acids in man. Curr Opin Clin Nutr Metab Care 2002. Read 2026-10-23.
- Burdge GC, Wootton SA. Conversion of alpha-linolenic acid to EPA, DPA and DHA in young women. Br J Nutr 2002. Read 2026-10-23.
- Williams CM, Burdge G. Long-chain n-3 PUFA: plant v. marine sources. Proc Nutr Soc 2006. Read 2026-10-23.
- Brenna JT et al. alpha-Linolenic acid supplementation and conversion to n-3 long-chain PUFA in humans. Prostaglandins Leukot Essent Fatty Acids 2009. Read 2026-10-23.
- Welch AA et al. Dietary intake and status of n-3 PUFA in fish-eaters, vegetarians and vegans: EPIC-Norfolk. Am J Clin Nutr 2010. Read 2026-10-23.
- Chamorro R et al. Vegetarian diets and their effect on n-3 PUFA status in humans: systematic review. Lipids 2026. Read 2026-10-23.
- NCCIH, Omega-3 Supplements: What You Need To Know. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.